Option Explicit
Const CstrOUDN = "OU=people,DC=example,DC=lan"
Const CstrUserName = "testuser"

fUserDel CstrOUDN, CstrUserName
WScript.Echo "end"

Function fUserDel( strOUDN, strUserName )
  Dim adsOU
  Set adsOU = GetObject( "LDAP://" & strOUDN )
  adsOU.Delete "user", "cn=" & strUserName
  fUserDel = True
End Function

Option Explicit
Const CstrUserDN = "CN=testuser,OU=people,DC=example,DC=lan"

fUserDel2 CstrUserDN
WScript.Echo "end"

Function fUserDel2( strUserDN )
  Dim adsUser, adsOU
  Set adsUser = GetObject( "LDAP://" & strUserDN )
  Set adsOU = GetObject( adsUser.Parent )
  adsOU.Delete "user", adsUser.Name
End Function

VBScript で Active Directory ユーザーの追加 | IADsContainer インターフェース